U.S. patent application number 12/226025 was filed with the patent office on 2009-07-09 for photosensitive resin composition for flexographic printing.
Invention is credited to Yoshifumi Araki, Kazuyoshi Yamazawa.
Application Number | 20090176176 12/226025 |
Document ID | / |
Family ID | 38581227 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090176176 |
Kind Code |
A1 |
Araki; Yoshifumi ; et
al. |
July 9, 2009 |
Photosensitive Resin Composition for Flexographic Printing
Abstract
There is provided a photosensitive resin composition for a
solvent-developing or thermally-developing flexographic printing
plate, the photosensitive resin composition comprising: (a) a block
copolymer containing a polymer block having conjugated diene as a
main component and a polymer block having a vinyl aromatic
hydrocarbon as a main component; (b) a photopolymerizable monomer;
(c) a photopolymerization initiator; and (d) an organosilicon
compound. A photosensitive resin composition for printing in which
the organosilicon compound is a silicone oil containing a specific
group is preferable, and a photosensitive resin composition for
printing in which the organosilicon compound is a silicone oil
containing an amino group or an aryl group is most preferable.
Inventors: |
Araki; Yoshifumi; (Tokyo,
JP) ; Yamazawa; Kazuyoshi; (Tokyo, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
38581227 |
Appl. No.: |
12/226025 |
Filed: |
April 5, 2007 |
PCT Filed: |
April 5, 2007 |
PCT NO: |
PCT/JP2007/057669 |
371 Date: |
October 6, 2008 |
Current U.S.
Class: |
430/286.1 |
Current CPC
Class: |
G03F 7/202 20130101;
G03F 7/36 20130101; G03F 7/033 20130101; G03F 7/0757 20130101 |
Class at
Publication: |
430/286.1 |
International
Class: |
G03F 7/075 20060101
G03F007/075 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2006 |
JP |
2006 106221 |
Claims
1. A photosensitive resin composition for a solvent-developing or
thermally-developing flexographic printing plate, comprising: (a) a
block copolymer comprising a polymer block having a conjugated
diene as a main component and a polymer block having a vinyl
aromatic hydrocarbon as a main component; (b) a photopolymerizable
monomer; (c) a photopolymerization initiator; and (d) an
organosilicon compound.
2. The photosensitive resin composition according to claim 1,
wherein the organosilicon compound (d) comprises a silicone oil
having a siloxane unit.
3. The photosensitive resin composition according to claim 2,
wherein the organosilicon compound (d) comprises an amino group or
an aryl group.
4. The photosensitive resin composition according to claim 2,
wherein the organosilicon compound (d) comprises an aralkyl
group.
5. The photosensitive resin composition according to claim 2,
wherein the organosilicon compound (d) comprises an amino
group.
6. The photosensitive resin composition according to claim 5,
wherein the organosilicon compound (d) has an amino group
equivalent of from 300 g/mol to 1,000 g/mol.
7. The photosensitive resin composition in any one of claims 1 to
6, wherein the block copolymer (a) comprises a polymer block having
butadiene as a main component and a polymer block having a vinyl
aromatic hydrocarbon as a main component.
8. The photosensitive resin composition in any one of claims 1 to
6, wherein the photosensitive resin composition has a content of
the organosilicon compound (d) in a range from 0.05% by weight to
1.0% by weight.
9. The photosensitive resin composition for a solvent-developing or
a thermally-developing flexographic printing plate according to any
one of claims 1 to 7, wherein the composition comprises 69 to 95%
by weight of the component (a), 1 to 20% by weight of the component
(b), 0.1 to 10% by weight of the component (c) and 0.05 to 1.0% by
weight of the component (d) based on 100% by weight of a sum of the
components (a), (b), (c) and (d) in the composition.
10. The photosensitive resin composition according to any one of
claims 1 to 9, wherein the photosensitive resin composition has a
vinyl content of not less than 40 mol % based on a total amount of
a liquid conjugated diene rubber contained in the composition.
11. The photosensitive resin composition according to any one of
claims 1 to 9, wherein the photosensitive resin composition
comprises a liquid conjugated diene rubber and wherein at least one
liquid conjugated diene rubber has a vinyl content of not less than
40 mol %.
12. The photosensitive resin composition according to any one of
claims 1 to 11, wherein the block copolymer (a) comprises an
alkylene unit.
13. The photosensitive resin composition according to any one of
claims 1 to 12, wherein at least one block copolymer (a) contained
in the photosensitive resin composition has a number-average
molecular weight of more than 200,000.
14. The photosensitive resin composition according to any one of
claims 1 to 13, wherein at least one photopolymerizable monomer (b)
comprises 2 mol of a methacrylate group per one molecule and
wherein the photosensitive resin composition comprises not less
than 2.0% by weight of the photopolymerizable monomer (b).
15. A photosensitive resin construct for a solvent-developing or
thermally-developing flexographic printing plate, the construct
comprising a laminated structure comprising: a support; and a layer
of the photosensitive resin composition according to any one of
claims 1 to 14 molded on a surface of the support.
16. The photosensitive resin construct for a solvent-developing or
thermally-developing flexographic printing plate according to claim
15, the construct comprising on the photosensitive resin
composition layer an ultraviolet-ray shielding layer which
comprises an infrared-ray sensitive substance and which is able to
ablate with an infrared laser.
17. A solvent-developing or thermally-developing flexographic
printing plate obtained by a process using the composition or the
construct according to any one of claims 1 to 16.
Description
TECHNICAL FIELD
[0001] The present invention relates to a photosensitive resin
composition for use in a flexographic printing plate.
BACKGROUND ART
[0002] Common photosensitive resin compositions for flexographic
printing generally contain a thermoplastic elastomer, a
photopolymerizable unsaturated monomer and a photopolymerization
initiator.
[0003] The construct for the flexographic printing plate includes a
polyester film or the like as a support, the photosensitive resin
composition provided thereon, and further includes, if required, a
protective layer for the purpose of smooth contacting with a
negative film provided on the photosensitive resin composition, or
an ultraviolet-ray shielding layer which contains an infrared-ray
sensitive substance and can be ablated with an infrared laser.
[0004] For making the flexographic printing plate from such the
photosensitive resin construct for the flexographic printing plate,
the whole construct surface is first subjected to ultraviolet-ray
exposure (back exposure) through the support to photopolymerize the
resin composition to make a uniform thin cured layer. Then, through
the negative film or directly from above the ultraviolet-ray
shielding layer, the photosensitive resin layer is subjected to
image exposure (relief exposure); and unexposed parts are washed
away with a developing solvent (hereinafter referred to as solvent
development), or the resin layer is brought into contact with an
absorbing layer such as a nonwoven fabric which can absorb the
unexposed parts heated at 40.degree. C. to 200.degree. C. and the
absorbing layer is removed to remove the unexposed parts
(hereinafter referred to as thermal development). Thereafter, the
resin construct surface on which irregularities are formed is
subjected to a post-exposure to make the flexographic printing
plate, which is a general manufacturing method thereof.
[0005] Printing using the photosensitive resin plate for
flexographic printing is performed with a system in which ink is
supplied by an ink-supplying roll or the like on convex parts of
the printing plate surface on which irregularities have been formed
and the resin plate is brought into contact with a matter to be
printed to transfer the ink on the surface of the convex parts to
the matter to be printed. In such flexographic printing, when
printing is continued for a long time, ink sometimes adheres to
shoulder parts of convex parts of a printing plate. Further, in
some case, the ink intrudes into concave parts of the printing
plate (hereinafter referred to as printing plate surface smear);
and a pattern is printed up to parts which are not included in an
original pattern. In such a case, printing is once suspended and
the printing plate surface must be wiped off with a cloth using a
washing liquid such as an alcohol, which is economically
disadvantageous.
[0006] Various methods of suppressing the printing plate surface
smear have been proposed.
[0007] Patent Document 1 proposes a method in which a mixed liquid
of an ink-repellent material and an aqueous resin is applied on a
printing plate surface.
[0008] Patent Document 2 proposes a method in which a
photosensitive resin for flexographic printing is brought into
contact with a solution containing a silicon compound or a fluorine
compound before the post-exposure process in platemaking of the
resin.
[0009] Patent Document 3 proposes a method in which a liquid
containing a modified-silicone compound or a fluorine compound is
brought into contact with a water-developing photosensitive resin
plate for letterpress printing after the exposure process in
platemaking of the plate.
[0010] The techniques of Patent Documents 1 to 3 above necessitate
an additional process in which a printing plate surface is brought
into contact with an ink-repellent component during the platemaking
process or after platemaking. Further, this contacting process
sometimes causes variations in the effect of preventing printing
plate surface smear, depending on contact time, contact area and
the like.
[0011] Patent Document 4 proposes a photosensitive resin
composition for printing base materials which contains a resin
having a molecular weight of not less than 1,000 and not more than
200,000 and having a polymerizable unsaturated group, and an
organosilicon compound having a Si--O bond and is capable of being
laser engraved. It proposes, as an example, a resin composition
containing a liquid resin having a polarity and a molecular weight
of 10,000 and containing an organosilicon compound having a Si--O
bond. The composition does not necessarily have sufficient
transparency and cold flow resistance because it aims at use as
printing base materials by laser engraving.
[0012] Patent Document 5 proposes a composition containing
fluorine, chlorine and silicon and containing a hydrophobic
compound copolymerizable with a polymerizable material. However,
since the applicable resin is limited to a liquid or pasty resin,
the composition has a problem of being inferior in image
reproducibility.
[0013] Patent Document 1: Japanese Patent Laid-Open No.
[0014] Patent Document 2: Japanese Patent Laid-Open No.
[0015] Patent Document 3: WO 05/64413
[0016] Patent Document 4: WO 05/70691
[0017] Patent Document 5: Japanese Patent Laid-Open No. 06
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0018] As described above, in the photosensitive resin construct
for flexographic printing, since an irregularity shape is
fabricated through an exposure (photopolymerization) process and a
development process, the transparency of the photosensitive resin
composition is important. Further, the photosensitive resin
construct for flexographic printing must undergo storage and
transportation before the exposure process and the development
process after manufacturing. Therefore, even if heat and load are
imparted to the construct in stages of storage and transportation,
the construct must have a property of maintaining its shape (cold
flow resistance). Hence, no method has been proposed, in which an
organosilicon compound is added into a photosensitive composition
containing a substantially hydrophobic block copolymer. This is
because when an organosilicon compound is added to a block
copolymer, the copolymer has problems of decreases in transparency
and cold flow resistance.
[0019] As described above, no photosensitive resin construct which
can prevent the printing plate surface smear while maintaining cold
flow resistance, transparency and image reproducibility has been
obtained.
[0020] Accordingly, an object of the present invention is to
provide a photosensitive resin composition simultaneously
satisfying (1) a high cold flow resistance of the photosensitive
resin construct, (2) a high transparency of the photosensitive
resin composition, (3) a high image reproducibility of the printing
plate, and (4) a high effect of preventing printing plate surface
smear of the printing plate.
Means for Solving the Problems
[0021] As a result of exhaustive studies to solve the problems
described above, the present inventors have found that the problems
described above can be solved, without adding any additional
process, by making a photosensitive resin composition containing an
organosilicon compound, thereby leading to the completion of the
present invention.
[0022] That is, the present invention is as follows:
1. A photosensitive resin composition for a solvent-developing or
thermally-developing flexographic printing plate, comprising:
[0023] (a) a block copolymer comprising a polymer block having a
conjugated diene as a main component and a polymer block having a
vinyl aromatic hydrocarbon as a main component;
[0024] (b) a photopolymerizable monomer;
[0025] (c) a photopolymerization initiator; and
[0026] (d) an organosilicon compound.
2. The photosensitive resin composition according to above 1,
wherein the organosilicon compound (d) comprises a silicone oil
having a siloxane unit. 3. The photosensitive resin composition
according to above 2, wherein the organosilicon compound (d)
comprises an amino group or an aryl group. 4. The photosensitive
resin composition according to above 2, wherein the organosilicon
compound (d) comprises an aralkyl group. 5. The photosensitive
resin composition according to above 2, wherein the organosilicon
compound (d) comprises an amino group. 6. The photosensitive resin
composition according to above 5, wherein the organosilicon
compound (d) has an amino group equivalent of from 300 g/mol to
1,000 g/mol. 7. The photosensitive resin composition in any one of
above 1 to 6, wherein the block copolymer (a) comprises a polymer
block having butadiene as a main component and a polymer block
having a vinyl aromatic hydrocarbon as a main component. 8. The
photosensitive resin composition in any one of above 1 to 6,
wherein the photosensitive resin composition has a content of the
organosilicon compound (d) in a range from 0.05% by weight to 1.0%
by weight. 9. The photosensitive resin composition for a
solvent-developing or a thermally-developing flexographic printing
plate according to any one of above 1 to 7, wherein the composition
comprises 69 to 95% by weight of the component (a), 1 to 20% by
weight of the component (b), 0.1 to 10% by weight of the component
(c) and 0.05 to 1.0% by weight of the component (d) based on 100%
by weight of a sum of the components (a), (b), (c) and (d) in the
composition. 10. The photosensitive resin composition according to
any one of above 1 to 9, wherein the photosensitive resin
composition has a vinyl content of not less than 40 mol % based on
a total amount of a liquid conjugated diene rubber contained in the
composition. 11. The photosensitive resin composition according to
any one of above 1 to 9, wherein the photosensitive resin
composition comprises a liquid conjugated diene rubber and wherein
at least one liquid conjugated diene rubber has a vinyl content of
not less than 40 mol %. 12. The photosensitive resin composition
according to any one of above 1 to 11, wherein the block copolymer
(a) comprises an alkylene unit. 13. The photosensitive-resin
composition according to any one of above 1 to 12, wherein at least
one block copolymer (a) contained in the photosensitive resin
composition has a number-average molecular weight of more than
200,000. 14. The photosensitive resin composition according to any
one of above 1 to 13, wherein at least one photopolymerizable
monomer (b) comprises 2 mol of a methacrylate group per one
molecule and wherein the photosensitive resin composition comprises
not less than 2.0% by weight of the photopolymerizable monomer (b).
15. A photosensitive resin construct for a solvent-developing or
thermally-developing flexographic printing plate, the construct
comprising a laminated structure
[0027] comprising: [0028] a support; and [0029] a layer of the
photosensitive resin composition according to any one of above 1 to
14 molded on a surface of the support. 16. The photosensitive resin
construct for a solvent-developing or thermally-developing
flexographic printing plate according to above 15, the construct
comprising on the photosensitive resin composition layer an
ultraviolet-ray shielding layer which comprises an infrared-ray
sensitive substance and which is able to ablate with an infrared
laser. 17. A solvent-developing or thermally-developing
flexographic printing plate obtained by a process using the
composition or the construct according to any one of above 1 to
16.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0030] The photosensitive resin composition according to the
present invention simultaneously satisfies a high preventing effect
on the printing plate smear of a printing plate while maintaining a
high cold flow resistance of the photosensitive resin construct, a
high transparency of the photosensitive resin composition, and a
high image reproducibility of the printing plate.
BEST MODE FOR CARRYING OUT THE INVENTION
[0031] Hereinafter, the present invention will be described in
detail centered on the preferable embodiments.
[0032] The photosensitive resin composition according to the
present invention comprises: (a) a block copolymer containing a
polymer block having a conjugated diene as a main component and a
polymer block having a vinyl aromatic hydrocarbon as a main
component; (b) a photopolymerizable monomer; (c) a
photopolymerization initiator; and (d) an organosilicon
compound.
[0033] The block copolymer (a) of the present invention must
contain at least one polymer block having conjugated diene as a
main component and at least one polymer block having a vinyl
aromatic hydrocarbon as a main component.
[0034] The term "as a main component" used throughout this
specification means a content of not less than 60% by weight in a
block. Above all, the content is preferably not less than 80% by
weight, more preferably 90% by weight.
[0035] Examples of the conjugated diene may include monomers such
as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene,
2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene,
3-butyl-1,3-octadiene and chloroprene. Above all, 1,3-butadiene is
preferable in view of wear resistance. These monomers may be used
singly or in combination of two or more thereof. The vinyl content
in the total butadiene amount in a polymer block having conjugated
diene as a main component, for example, the content of
1,2-butadiene and 3,4-isoprene, is not especially limited. The
vinyl content is preferably 5 mol % to 50 mol % in view that it
provides a high formability of fine images of a printing plate and
a high chipping resistance of the printing plate. The content is
more preferably in a range from 8 mol % to 50 mol %, still more
preferably from 10 mol % to 40 mol %.
[0036] The number-average molecular weight of the polymer block
having conjugated diene as a main component is preferably from
20,000 to 250,000, because it provides a high cold flow resistance
and a high chipping resistance of convex parts of a printing plate.
The molecular weight is more preferably from 30,000 to 200,000,
still more preferably from 40,000 to 150,000.
[0037] For providing a high solvent ink resistance, the block
copolymer (a) preferably comprises an alkylene unit. The
introducing method of an alkylene unit is not especially limited,
but includes a method in which raw material monomers for a block
copolymer is polymerized with monoolefins such as ethylene and
butylene and a method in which a conjugated diene polymer block is
hydrogenated. Above all, hydrogenation of the conjugated diene
block polymer is preferable in view of its availability. The
content of the alkylene unit in the block copolymer (a) is
preferably not less than 5 mol % in view of providing a high
solvent ink resistance, and preferably not more than 50 mol % in
view of providing a high chipping resistance of convex parts of a
printing plate. The content is more preferably in a range from 10
mol % to 35 mol %, still more preferably from 10 mol % to 25 mol
%.
[0038] Since a high image reproducibility and a higher chipping
resistance of convex parts of the printing plate are provided, the
alkylene unit described above is preferably contained in the
polymer block having butadiene as the main component. More
preferably, the polymer block moiety having butadiene as a main
component is hydrogenated, and contains all of a 1,4-butadiene
unit, a 1,2-butadiene (vinyl) unit and a butylene (alkylene) unit.
More preferably, the polymer block having butadiene as the main
component contains the 1,4-butadiene unit in a range from 25 mol %
to 70 mol %, the 1,2-butadiene (vinyl) unit in a range from 0 mol %
to 50 mol % and the butylene unit in a range from 10 mol % to 50
mol %.
[0039] The conjugated diene, vinyl contents of the conjugated diene
and the contents and ratios of the vinyl aromatic hydrocarbon can
be measured using a nuclear magnetic resonance apparatus
(.sup.1H-NMR).
[0040] Examples of the vinyl aromatic hydrocarbon may includes
monomers such as styrene, t-butylstyrene, divinylbenzene,
1,1-diphenylstyrene, N,N-dimethyl-p-aminoethylstyrene,
N,N-diethyl-p-aminoethylstyrene, vinylpyridine, p-methylstyrene,
tertiarybutylstyrene, .alpha.-methylstyrene and
1,1-diphenylethylene. Above all, styrene is preferable in view of a
photosensitive resin construct capable of being molded smoothly at
a relatively low temperature (hereinafter referred to as high
moldability). These monomers may be used singly or concurrently in
two or more thereof.
[0041] The number-average molecular weight of the polymer block
having a vinyl aromatic hydrocarbon as a main component is
preferably not more than 100,000 in view that fine images can be
formed on a printing plate in a high reproducibility, and
preferably not less than 3,000 because of the photosensitive resin
construct having a high cold flow resistance. The molecular weight
is more preferably in a range from 5,000 to 80,000, still more
preferably from 5,000 to 60,000.
[0042] The content of a vinyl aromatic hydrocarbon in the block
copolymer is preferably not more than 25% by weight in view of a
high moldability of the photosensitive resin composition, a high
chipping resistance of convex parts of a printing plate and a high
maintainability of the printing plate hardness when a flexographic
ink is adhered to the printing plate. On the other hand, the
content is preferably not less than 13% by weight in view of a high
cold flow resistance of the photosensitive resin construct. The
content is more preferably in a range from 15% by weight to 24% by
weight, still more preferably from 16% by weight to 23% by
weight.
[0043] As required, a block as a third component may be
contained.
[0044] The number-average molecular weight of at least one block
copolymer (a) contained in the photosensitive resin composition is
preferably not less than 200,000 because of providing a high cold
flow resistance of the photosensitive resin construct and a high
chipping resistance of convex parts of a printing plate. The
molecular weight is more preferably not less than 230,000.
[0045] The content of the block copolymer (a) in the photosensitive
resin composition is preferably not less than 69% by weight based
on 100% by weight of the sum of the components (a), (b), (c) and
(d) in the photosensitive resin composition according to the
present invention in view of a high cold flow resistance of the
photosensitive resin construct and a high chipping resistance of
convex parts of a printing plate, and preferably not more than 95%
by weight because of the easy moldability of the photosensitive
resin composition. The content is more preferably in a range from
75% by weight to 90% by weight, still more preferably from 80% by
weight to 90% by weight.
[0046] The photopolymerizable monomer (b) of the present invention
may includes esters of acrylic acid, methacrylic acid, fumaric acid
and maleic acid; derivatives of acrylamide and methacrylamide;
allyl esters, styrene and its derivatives; and N-substituted
maleimide compounds.
[0047] Specific examples may include diacrylates and
dimethacrylates of alkanediols such as hexandiol and nonanediol;
diacrylates and dimethacrylates of ethylene glycol, diethylene
glycol, propylene glycol, dipropylene glycol, polyethylene glycol
and butylene glycol; trimethylolpropane tri(meth)acrylate,
dimethyloltricyclodecane di(meth)acrylate, isoboronyl
(meth)acrylate, phenoxypolyethylene glycol (meth)acrylate,
pentaerythritol tetra(meth)acrylate,
N,N'-hexamethylenebisacrylamide and
N,N'-hexamethylenebismethacrylamide, styrene, vinyltoluene,
divinylbenzene, diacryl phthalate, triallyl cyanurate, fumaric acid
diethyl ester, fumaric acid dibutyl ester, dioctyl fumarate ester,
fumaric acid distearyl ester, fumaric acid butyl octyl ester,
fumaric acid diphenyl ester, fumaric acid dibenzyl ester, maleic
acid dibutyl ester, maleic acid dioctyl ester, fumaric acid
bis(3-phenylpropyl) ester, fumaric acid dilauryl ester, fumaric
acid dibehenyl ester and N-laurylmaleimide. These may be used
singly or in combination of two or more thereof.
[0048] The content of the phtopolymerizable monomer (b) in the
photosensitive resin composition is preferably not less than 1% by
weight based on 100% by weight of the sum of the components (a),
(b), (c) and (d) in the photosensitive resin composition according
to the present invention in view of the high chipping resistance of
convex parts of the printing plate, and preferably not more than
20% by weight in view of a high cold flow resistance of the
photosensitive resin construct and a high flexibility of the
printing plate. The content is preferably in the range from 2% by
weight to 15% by weight, still more preferably from 4% by weight to
12% by weight.
[0049] In view of the higher chipping resistance of convex parts of
the printing plate, the resin composition preferably contains not
less than 2.0% by weight of a monomer having 2 mol of a
methacrylate group.
[0050] The photopolymerization initiator (c) of the present
invention is a compound which absorbs the light energy and
generates radicals, and well-known various types thereof can be
used. Various types of organic carbonyl compounds, especially
aromatic carbonyl compounds, are suitable.
[0051] Specific examples may include benzophenone,
4,4-bis(diethylamino)benzophenone; t-butylanthraquinone,
2-ethylanthraquinone; thioxanthones such as
2,4-diethylthioxanthone, isopropylthioxanthone and
2,4-dichlorothioxanthone; acetophenones such as
diethoxyacetophenone, 2,2-methoxy-phenylacetophenone,
2-hydroxy-2-methyl-1-phenylpropane-1-one, benzyl dimethyl ketal,
1-hydroxycyclohexyl-phenyl ketone,
2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoin
ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin
isopropyl ether and benzoin isobutyl ether; acylphosphine oxides
such as 2,4,6-trimethylbenzoyl diphenyl phosphine oxide,
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and
bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; methylbenzoyl
formate; 1,7-bisacridinylheptane; and 9-phenylacridine. These may
be used singly or in combination of two or more thereof.
[0052] The content of the photopolymerization initiator (c) is
preferably in a range from 0.1% by weight to 10% by weight based on
100% by weight of the sum of the components (a), (b), (c) and (d)
in the photosensitive resin composition according to the present
invention in view of a high reproducibility of fine points and
characters and the transmittance of active light such as
ultraviolet rays being held in a preferable range. The content is
more preferably in a range from 0.5% by weight to 5% by weight.
[0053] A degradation-type photopolymerization initiator and a
hydrogen-abstraction-type photopolymerization initiator may be
concurrently used. The amount of the hydrogen-abstraction-type
photopolymerization initiator in the photosensitive resin
composition is preferably not more than 1.0% by weight because of a
high image reproducibility and wear resistance of a printing plate.
The amount is more preferably not more than 0.5% by weight.
[0054] The organosilicon compound (d), which is essential in the
present invention, includes silicone oils containing a siloxane
unit (hereinafter, simply referred to as silicone oil) and silane
coupling agents, silane compounds, silicone rubbers and silicone
resins. Above all, silicone oils are preferable in view that the
transparency of the photosensitive resin composition and the cold
flow resistance of the photosensitive resin construct can be
achieved in a balanced manner.
[0055] The molecular structure is not especially limited, but
preferable compounds may include those having polyalkylsiloxane
such as polydimethylsiloxane and polydiethylsiloxane in their main
chain. Compounds having a polysiloxane structure in a part of their
molecule may be used. Further, compounds in which a specific
organic group is introduced to the polysiloxane structure may be
used. Specifically usable are compounds in which organic groups are
introduced to side chains of polysiloxane, compounds in which
organic groups are introduced to both terminals of polysiloxane,
compounds in which an organic group is introduced to one terminal
of polysiloxane, compounds in which organic groups are introduced
to both side chains and terminals of polysiloxane, and the
like.
[0056] Specific examples of organic groups introduced into
polysiloxane structures may include an amino group, a carboxyl
group, a carbinol group, an aryl group, an alkyl group, an
alkoxycarbonyl group, an alkoxy group, a linear or branched alkyl
group substituted with at least one aryl group and a
polyoxyalkylene group.
[0057] Among these, organic groups containing at least an amino
group or an aryl group are preferable in view of a high
transparency and image reproducibility of the photosensitive resin
composition.
[0058] The amino group may include a primary to tertiary monoamino
group or diamino group. The aryl group may include a phenyl group,
a tolyl group, a xylyl group, a biphenyl group, a naphthyl group,
an anthryl group, a pyrenyl group and a phenanthryl group. A linear
or branched alkyl group substituted with, for example, an aryl
group such as a methylstyryl group or a styryl group is preferable.
Further, an organic group in which a hydrogen atom bonded to an
aromatic carbon of an aryl group is substituted with another
functional group may be used. Further, an organic group in which a
part of or the whole of hydrogen atoms bonded to the organic groups
is substituted with halogen atoms such as fluorine atoms, chlorine
atoms and bromine atoms may be used.
[0059] Above all these, an organic group containing an amino group
or an aralkyl group in which at least one hydrogen atom of an alkyl
group is substituted with an aryl group is more preferable. Among
the aralkyl groups, aralkyl groups having a hydrogen atom bonded to
a carbon atom to which a phenyl group is directly bonded, that is,
aralkyl groups such as methylstyryl having a hydrogen atom
(hereinafter, abbreviated as .alpha.-position hydrogen) bonded to
the .alpha.-position carbon of a straight chain compound are
especially preferable in view of a high effect on preventing the
printing plate surface smear of the printing plate.
[0060] Further, silicone oils having an amino group as the organic
group are most preferable because of the high cold flow resistance
of the photosensitive resin construct and a long lasting effect of
preventing the printing plate surface smear of the printing plate.
Among them, the organic group preferably contains an aliphatic
amine and the amino group preferably has an amino equivalent weight
(g/mol) in a silicone oil in a range from 300 g/mol to 1,000 g/mol
because of a high image reproducibility of the printing plate. The
amino group equivalent weight is more preferably in a range from
350 g/mol to 800 g/mol. Silicone oils having polysiloxane as a main
skeleton and at least an amino group at the terminal are most
preferable.
[0061] The amino group equivalent weight can be calculated
according to the following method. First, about 1 g of a silicone
oil containing an aliphatic amine is weighed in a clean Mayer flask
(volume: 200 ml); and 50 ml of a mixed solution of isopropyl
alcohol and xylene in 1:1 is added thereto. The mixture is fully
stirred, and thereafter, the solution is measured using a 0.1-N
hydrochloric acid aqueous solution by an automatic titrator. The
amino group equivalent weight is calculated by the following
equation from the obtained measurement value.
Amino group equivalent weight=(sample amount
(g)).times.10,000)/(hydrochloric acid titration amount
(ml).times.titer)
[0062] The structure and composition of polysiloxane can be
measured by .sup.1H-NMR or 29Si-NMR. The measurement condition of
.sup.1H-NMR is as follows. JNM-LA400 (trade name, made by JEOL
Ltd.) was used as a measurement instrument of .sup.1H-NMR;
deuterated chloroform was used as a solvent; the sample
concentration was 50 mg/ml; the observing frequency was 400 MHz;
the chemical shift was based on TMS (tetramethylsilane); the pulse
delay was 2.904 sec; the number of times of the scan was 64; the
pulse width was 45.degree.; and the measurement temperature was
26.degree. C.
[0063] The condition of 29Si--NMR is as follows. JNM-LA400 (trade
name, made by JEOL Ltd.) was uses as a measurement instrument of
29Si--NMR; the observed nucleus was 29Si; the observing frequency
was 79.4 MHz; the pulse width was 45.degree.; and the integrating
times was 6,000. Tris(2,4-pentanedionate)chromium(III)) was used as
a relaxation reagent.
[0064] Commonly available commercial silicone oils may include, for
example, various types of organic group-substituted silicone oils
made by Shin-Etsu Chemical Co., Ltd., Wacker Asahikasei Silicone
Co., Ltd., GE Toshiba Silicones Co., Ltd., and Dow Corning Toray
Silicone, Inc.
[0065] The number-average molecular weight of the organosilicon
compound (d) is preferably not more than 15,000 because of the high
transparency of the photosensitive resin composition and the high
image reproducibility of the printing plate. The molecular weight
is more preferably not more than 10,000, still more preferably
3,000.
[0066] The content of the organosilicon compound (d) in the
photosensitive resin composition according to the present invention
is preferably not more than 1.0% by weight based on 100% by weight
of the sum of the components (a), (b), (c) and (d) in the
photosensitive resin composition according to the present invention
because of the high transparency of the photosensitive resin
composition and the high image reproducibility of the printing
plate. On the other hand, the content is preferably not less than
0.05% by weight because of the high effect of preventing the
printing plate surface smear of the printing plate. The content is
more preferably from 0.1% by weight to 0.8% by weight, still more
preferably in a range from 0.15% by weight to 0.6% by weight.
[0067] The organosilicon compound (d) of the present invention is
useful in the photosensitive resin construct having an
ultraviolet-ray shielding layer. Since the photosensitive resin
construct having an ultraviolet-ray shielding layer is largely
susceptible to the oxygen inhibition in an exposure process of a
resin component unlike the general photosensitive resin construct
using a negative film, the curing of the printing plate surface is
liable to become incomplete. On the other hand, in the
photosensitive resin composition containing an organosilicon
compound, since ink-repellent components are easily removed on
development, the composition has a high effect of preventing the
printing plate surface smear of the printing plate, which can
therefore solve the above-mentioned problem.
[0068] To the photosensitive resin composition according to the
present invention, in addition to the above-mentioned essential
components, various types of auxiliary additives may be added, such
as plasticizers, thermal polymerization inhibitors, ultraviolet
absorbents, halation preventing agents, light stabilizers and light
luminescence tags (substances excited by an external energy source
and emitting the obtained energy in a form of light and/or
radiation).
[0069] The plasicizers may include hydrocarbon oils such as
naphthene oils and paraffin oils; conjugated diene rubbers having
liquid diene as a main component, such as liquid
acrylicnitrile-butadiene copolymers and liquid styrene-butadiene
copolymers; and polystyrenes having a number-average molecular
weight of not more than 2,000, sebacic acid ester and phthalic
ester. A photopolymerizable reaction group may be imparted to these
plasticizers.
[0070] Above all these, conjugated diene rubbers having a viscosity
of not more than 2,000 Pa.s at 30.degree. C., namely having a
liquid diene as a main component, is preferable in view of the high
flexibility and the high image reproducibility of the printing
plate. The viscosity can be measured according to JIS K7117.
[0071] As the dienes, isoprene and/or butadiene is (are) preferable
because of their easy availability, and butadiene is more
preferable because of providing the high chipping resistance. The
diene rubbers having a viscosity of not more than 2,000 Pa.s at
30.degree. C. and a liquid diene as a main component may be used
concurrently in two or more thereof.
[0072] The vinyl content based on the total amount of diene
contained in at least one conjugated diene rubber having a
viscosity of not more than 2,000 Pa.s at 30.degree. C. is
preferably not less than 40 mol % because of providing the high
reproducibility of fine images and the high chipping resistance.
The content is more preferably not less than 60 mol %, still more
preferably not less than 80 mol %. The vinyl content in the
conjugated diene having a viscosity of not more than 2,000 Pa.s at
30.degree. C. can be measured by .sup.1H-NMR (nuclear magnetic
resonance spectrum) described above.
[0073] The vinyl content based on the total amount of diene in the
conjugated diene rubber having a viscosity of not more than 2,000
Pa.s at 30.degree. C. is preferably not less than 40 mol % because
of the high reproducibility of fine images, the high chipping
resistance of convex parts of the printing plate and a high ink
resistance. The content is more preferably not less than 60 mol %,
still more preferably not less than 70 mol %.
[0074] A lower number-average molecular weight (Mn) of the
conjugated diene rubber is more preferable in view of the
handleability and the compatibility with the photosensitive resin
composition. On the other hand, a higher one is more preferable
because of the high chipping resistance. The molecular weight is
preferably in a range from 1,000 to 50,000, more preferably from
2,000 to 30,000, still more preferably from 3,000 to 20,000.
[0075] The number-average molecular weight (Mn) in the present
invention is a molecular weight in terms of polystyrene measured by
gel permeation chromatography (GPC). The measurement was performed
using LC-10 (trade name, made by Shimadzu Corp.) as the measurement
instrument and two columns of TSKgelGMHXL (4.6 mmID.times.30 cm) as
the column, at an oven temperature of 40.degree. C., and using
tetrahydrofuran (1.0 ml/min) as the solvent.
[0076] Hereinafter, a method for fabricating a construct using the
photosensitive resin composition for flexographic printing
according to the present invention will be described.
[0077] The photosensitive resin construct for flexographic printing
generally has a supporting layer, and at least one layer of a
photosensitive resin layer thereon, and as required, a protecting
layer, an ultraviolet-ray shielding layer which can be cut away
with an infrared laser, or the like thereon.
[0078] The support may includes, for example, polypropylene films,
polyethylene films, polyester films such as polyethylene
terephthalate and polyethylene naphthalate, and polyamide films.
Size-stable polyester films having a thickness in a range from 75
to 300 .mu.m are preferable. An adhesive layer is preferably
provided on the support. The adhesive layer may include, for
example, compositions having a binder polymer such as a
thermoplastic elastomer, and an adhesive active component such as
an isocyanate compound or an ethylenic unsaturated compound. To the
adhesive layer, various types of auxiliary additives may be further
added, such as plasticizers, thermal polymerization inhibitors,
ultraviolet-ray absorbents, halation preventing agents, light
stabilizers, photopolymerization initiators, photopolymerizable
monomers and dyes. For providing a more adhesive force between the
adhesive layer and the support, at least one layer of an underlying
layer is more preferably provided.
[0079] Since the photosensitive resin composition generally has
tackiness, a solvent-soluble protecting layer may be provided on
the resin layer surface for improving the contactability with a
negative film superposed on the composition in plate making, or for
enabling the reuse of the negative film. The protecting layer must,
for example, be composed of a substance soluble in a solvent used
as a washout liquid, be thin, and have a flexibility. The examples
may include a crystalline 1,2-polybutadiene, a soluble polyamide, a
partially saponified polyvinyl acetate and a cellulose ester. Above
all, the soluble polyamide is preferable. These substances may be
dissolved in an appropriate solvent and coated directly on the
photosensitive resin layer surface, or may be once coated on a film
such as a polyester or polypropylene film, and laminated and
transferred together with the film on the photosensitive resin
layer.
[0080] By making this protecting layer of an ultraviolet-ray
shielding layer containing an infrared-ray sensitive substance and
directly cutting away the layer by an infrared-ray laser
(hereinafter referred to as laser drawing), the layer itself may be
used as a negative. In either case, when unexposed parts are washed
out after the completion of the exposure, the protecting layer is
simultaneously removed. The ultraviolet-ray shielding layer
comprises a binder polymer, an infrared-ray sensitive substance and
a non-infrared radiation shielding substance. The binder polymer
may include, for example, polyamides, polyesters and copolymers
composed of a monovinyl-substituted aromatic hydrocarbon and a
conjugated diene. Above all, copolymers composed of a
monovinyl-substituted aromatic hydrocarbon such as styrene,
.alpha.-methylstyrene or vinyltoluene and a conjugated diene such
as 1,3-butadiene or isoprene are preferable. In the case where a
non-infrared radiation shielding layer is constituted using the
binder polymer, the layer has a high affinity for the
photosensitive resin composition and a favorable adhesiveness.
[0081] In the case of using polyester as the binder polymer, the
number-average molecular weight thereof is preferably not less than
300 and not more than 10,000.
[0082] Examples of especially preferable polyesters may include
those synthesized from an alkane diol and adipic acid, those
synthesized from an alkane diol and phthalic acid,
polycaprolactones and combinations of two or more of these
polyesters. The polyester may contain various functional groups
such as an amino group, a nitro group, a sulfonic acid group and a
halogen in a range of not damaging the compatibility with the
binder polymer.
[0083] For the infrared-ray sensitive substance, a single substance
or a compound having a strong absorption in a range of 750 to 2,000
nm is commonly used. Such an example may include inorganic pigments
such as carbon black, graphite, copper chromite and chrome oxide,
and dyes such as polyphthalocyanine compounds, cyanine dyes and
metal thiolate dyes. These infrared-ray sensitive substances are
added in a range of imparting the sensitivity capable of cutting
away the protecting layer with a laser beam. The addition of 10 to
80% by weight is generally effective. For the shielding substance
of a non-infrared radiation, a substance which reflects or absorbs
the radiation such as ultraviolet rays can be used. Absorbents of
radiation such as ultraviolet rays, carbon black and graphite are
preferable examples and the addition amount is set so as to achieve
a predetermined optical density. The addition is generally needed
such that the optical density is not less than 2, preferably not
less than 3.
[0084] An infrared-ray laser of 750 to 2,000 nm in wavelength can
be used. This type of infrared-ray laser generally may include a
semiconductor laser of from 750 to 880 nm and a Nd-YAG laser of
1,060 nm.
[0085] The resin construct for the flexographic printing plate
according to the present invention can be prepared by any of
various methods. For example, there are following methods. A method
may involve dissolving and mixing raw materials of the
photosensitive resin composition in an appropriate solvent such as
chloroform, tetrachloroethylene, methyl ethyl ketone or toluene,
casting the solution into a BR> mold and evaporating the solvent
to make a plate-like construct. A method may involve, without using
any solvent, kneading the mixture in a kneader, roll mill or screw
extruder, and then molding it into a predetermined thickness by a
calendar roll or press. However, the present invention is not
limited to these preparation methods.
[0086] For providing the protecting layer or the ultraviolet-ray
shielding layer on the surface of the photosensitive resin layer,
raw materials thereof may be dissolved or dispersed in an
appropriate solvent with forced stirring by stirring blades or
ultrasonic stirring; or the raw materials are pre-kneaded using an
extruder or kneader and then dispersed or dissolved in an
appropriate solvent, and the dispersion or solution may be coated
directly on the photosensitive resin layer. Further, a cover sheet
composed of polyester, polypropylene or the like may be provided on
the protecting layer or the ultraviolet-ray shielding layer.
Alternatively, a solution for the protecting layer or the
ultraviolet-ray shielding layer is coated on a cover sheet to make
a protecting film, and then the protecting film may be laminated or
pressed on the photosensitive layer to transfer the protecting
film.
[0087] The protecting film and the support are typically adhered to
the photosensitive resin composition by roll lamination after a
sheet of the photosensitive resin composition is molded, and
heat-pressed after the lamination, thereby providing a
photosensitive resin layer with a higher thickness precision.
[0088] For making the flexographic printing plate from the
photosensitive resin construct for the flexographic printing plate,
the following method is generally employed. First, the whole
surface of the construct is subjected to ultraviolet-ray exposure
through the support of the construct (back exposure), and the
photosensitive resin composition is cured to make a uniform thin
cured layer. Then, a negative film is laid on the photosensitive
resin composition layer; and the photosensitive resin layer surface
is subjected to image exposure (relief exposure) through the
negative film laid on the photosensitive resin composition layer,
or directly from above an ultraviolet-ray shielding layer after the
shielding layer provided on the photosensitive resin composition
layer is subjected to laser drawing. Then, unexposed parts are
washed out with a developing solvent, or unexposed parts heated at
40.degree. C. to 200.degree. C. are brought into contact with an
absorbing layer capable of absorbing the unexposed parts and the
absorbing layer is removed to remove the unexposed parts.
Thereafter, the photosensitive resin layer is subjected to
post-exposure to manufacture the flexographic printing plate.
[0089] Either of the exposure (relief exposure) from the negative
film side or ultraviolet-ray shielding layer side and the exposure
from the support side (back exposure) may be first performed, or
both may be simultaneously performed. Exposure light sources may
include a high pressure mercury lamp, an ultraviolet fluorescent
lamp, a carbon arc lamp and a xenon lamp.
[0090] The developing solvents used for developing unexposed parts
with a solvent may include esters such as heptyl acetate and
3-methoxybutyl acetate; hydrocarbons such as petroleum fractions,
toluene and decalin; mixtures of a chlorine-based organic solvent
such as tetrachloroethylene with alcohols such as propanol,
butanol, and pentanol. Washout of unexposed parts is performed
using injection from a nozzle or brushing by a brush.
[0091] The absorbing layer of thermal development may include
nonwoven materials, paper stocks, fibrous tissues, open-cell foams
and porous materials. Preferable examples of the absorbing layers
may include nonwoven materials composed of nylon, polyester,
polypropylene and polyethylene, and combinations of these nonwoven
materials. The especially preferable examples of the absorbing
layer may include a nonwoven continuous web of nylon or
polyester.
[0092] The post-exposure generally uses a method in which light of
not more than 300 nm in wavelength is irradiated to the surface. As
required, light of more than 300 nm may also be concurrently
used.
[0093] The flexographic printing plate is brought into contact with
a matter to be printed on a printing machine during printing, and
too flexible a printing plate cannot provide a finely printed
matter due to deformation by compression; and too hard one cannot
provide a printed matter having a uniform solid surface; therefore,
the Shore A hardness of the printing plate of 3 mm in thickness is
preferably in a range from 50.degree. to 68.degree.. This hardness
can be achieved, for example, by adjusting the amounts of a block
copolymer (a), a phtopolymerizable monomer (b), and as required, a
plasticizer and the like.
[0094] The resin composition according to the present invention is
useful for both the solvent development and the thermal
development, but is suitably usable for the solvent development
especially in view of the high image reproducibility of the
printing plate.
EXAMPLES
[0095] Hereinafter, the present invention will be described more
specifically by way of examples and comparative examples, but the
scope of the present invention is not limited to these
examples.
(1) Manufacture of a Block Copolymer (a)
[0096] The interior of a 10-L stainless steel-made reactor vessel
with a jacket and a stirrer was replaced fully by nitrogen;
thereafter, 7,000 cc of cyclohexane, 1 g of tetrahydrofuran, 3.5 g
of N,N,N',N'-tetramethylethylenediamine and 170 g of styrene were
charged thereto. Warm water was passes through the jacket and the
temperature of the contents were set at about 70.degree. C.
Thereafter, n-butyllithium cyclohexane solution (net 1.15 g) was
added thereto and polymerization of styrene was started. After
styrene had been completely polymerized, 830 g of butadiene
(1,3-butadiene) was added thereto and the polymerization was
continued. At 4 min after the polymerization of butadiene had been
completely finished, 0.83 g of tetramethoxysilane was added for the
coupling reaction. A part of the obtained block copolymer solution
was sampled and thereafter, the solvent was removed by heating. The
polymer had a styrene content of 17% by weight, and a 1,2-vinyl
content in the butadiene polymer block of 55 mol %. The
number-average molecular weight was 240,000. The styrene content
was measured using ultraviolet spectroscopy (UV). The vinyl content
was measured using infrared spectroscopy (IR), and calculated by
the Hampton method. The number-average molecular weight was a
molecular weight in terms of polystyrene measured by gel permeation
chromatography (GPC). The measurement was performed using LC-10
(trade name, made by Shimadzu Corp.) as the measurement instrument,
two columns of TSKgelGMHXL (4.6 mmID.times.30 cm) as the column and
tetrahydrofuran (1.0 ml/min) as the solvent, and at an oven
temperature of 40.degree. C.
[0097] Next, using the block copolymer solution from which the
solvent had been removed, the hydrogenation was performed at a
temperature of 70.degree. C. with bis(cyclopentadienyl)titanium
chloride and n-butyllithium as hydrogenation catalysts. The
hydrogenation rate was controlled by measuring a supplied hydrogen
gas amount by a flow meter and stopping the gas supply at the time
when the target hydrogenation rate had been attained. Thereafter,
10 g of water was added and the mixture was stirred, and then, 3.0
g of n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate
and 1.5 g of 2,4-bis(n-octylthiomethyl)-O-cresol were added. The
obtained solution was subjected to steam stripping to remove the
solvent to thereby obtain a hydrous crumb. Successively, the
hydrous crumb was dehydrated and dried by a hot roll to thereby
obtain a sample of a block copolymer containing 45 mol % of a
1,4-butadiene unit, 35 mol % of the 1,2-vinyl content and 20 mol %
of a butylene unit in the butadiene polymer block. This sample was
referred to as Sample (a). The hydrogenation rate was confirmed
using a nucleus magnetic resonance apparatus (NMR).
(2) Organosilicon Compounds (d)
[0098] For Examples 1 to 9, the following seven types of silicone
oils were used.
KF-8010 (trade name, made by Shin-Etsu Chemical Co., number-average
molecular weight: not more than 1,000, amino group equivalent: 450
g/mol, and organic groups having an amino group are introduced to
both terminals of a polysiloxane.) X-22-161B (trade name, made by
Shin-Etsu Chemical Co., number-average molecular weight: 3,000,
amino group equivalent: 1,500 g/mol, and organic groups having an
amino group are introduced to both terminals of a polysiloxane.)
KF-410 (trade name, made by Shin-Etsu Chemical Co., Ltd.,
number-average molecular weight: 8,000, and organic groups having a
methylstyryl group are introduced to the side chains of a
polysiloxane) SH-710 (trade name, made by Dow Corning Toray
Silicone Co., Ltd., number-average molecular weight: 1,000, and
phenyl groups are introduced to the side chains of a polysiloxane.)
X-22-4272 (trade name, made by Shin-Etsu Chemical Co., Ltd.,
number-average molecular weight: 2,240, and ether groups are
introduced to both terminals of a polysiloxane.) X-22-3710 (trade
name, made by Shin-Etsu Chemical Co., Ltd., number-average
molecular weight: 1,450, and carboxyl groups are introduced to the
terminals of a polysiloxane.) KF-96-100CS (trade name, made by
Shin-Etsu Chemical Co., Ltd., number-average molecular weight:
3,130, and not-modified dimethylpolysiloxane)
(3) Manufacture of Photosensitive Resin Compositions and
Photosensitive Resin Constructs.
[0099] Photosensitive resin compositions were obtained by charging
raw materials, so as to make the compositions shown in Examples 1
to 9 and Comparative Examples 1 to 3, in a kneader whose interior
atmosphere was replaced by nitrogen, and mixing the each mixture at
140.degree. C. for 40 min.
[0100] A solution for an adhesive layer to be coated on a support
was prepared as a solution of 25% in solid content by dissolving,
in toluene, 55 parts by mass of Tufprene 912, which is a block
copolymer of styrene and 1,3-butadiene, (trade name, made by Asahi
Kasei Chemicals Corp.), 38 parts by mass of a paraffin oil (its
average carbon number: 33, its average molecular weight: 470, its
density at 15.degree. C.: 0.868), 2.5 parts by mass of
1,9-nonanediol diacrylate, 1.5 parts by mass of
2,2-dimethoxy-phenylacetophenone, 3 parts by mass of Epoxy Ester
3000M (trade name, made by Kyoueisha Chemical Co., Ltd.), and 1.5
parts by mass of VALIFAST YELLOW 3150 (trade name, made by Orient
Chemical Industries, Ltd.), in proportion. Thereafter, the solution
was applied on one surface of a polyester film of 100 .mu.m in
thickness using a knife coater so as to have an ultraviolet-ray
transmittance of 10%, and dried at 80.degree. C. for 1 min to
thereby obtain a support having an adhesive layer. The UV
transmittance of the support was obtained by using an
ultraviolet-ray exposure machine AFP-1500 (trade name, made by
Asahi Kasei Chemicals Corp.) and measuring the transmission
intensity by a UV luminometer MO-2 (trade name, made by ORC
Manufacturing Co., Ltd., using UV-35 filter), and calculating the
transmittance.
[0101] Then, a manufacturing method of a protecting film will be
described. 65% by weight of Asaflex 810, which is a block copolymer
of styrene and 1,3-butadiene, (trade name, made by Asahi Kasei
Chemicals Corp.) and 35% by weight of a carbon black as an
infrared-ray sensitive substance were kneaded by a kneader, and cut
into pellets; thereafter, 90 parts by mass of the pellet and 10% by
mass of 1,6-hexanediol adipate were dissolved in a mixed solvent of
ethyl acetate/butyl acetate/propylene glycol monomethyl ether
acetate prepared in a weight ratio of 50/30/20 utilizing ultrasonic
to thereby prepare a homogeneous solution of 12% by weight in solid
content. Then, the solution was applied on a polyester film serving
as a cover sheet of 100 .mu.m in thickness using a knife coater
such that the coated amount after drying was 4 to 5 g/m.sup.2, and
dried at 80.degree. C. for 1 min to thereby obtain a protecting
film having an ultraviolet-ray shielding layer capable of being
ablated with infrared rays. The optical density of the protecting
film was measured by DM-500 (trade name, made by Dainippon Screen
Mfg. Co., Ltd.), and was 3 to 4. The photosensitive resin
composition was interposed and laminated between the surface of the
obtained support on which the adhesive had been coated and the
surface of the protecting film on which the ultraviolet-ray
shielding layer had been coated, then pressed, using a spacer of 3
mm, at 130.degree. C. for 4 min under a pressure of 200 kg/cm.sup.2
by a heating press, and then cooled to thereby obtain a
photosensitive resin construct of 25 cm long.times.25 cm
wide.times.3 mm thick.
(4) Manufacture of a Flexographic Printing Plate
[0102] The cover sheet of the photosensitive resin construct
obtained in (3) was peeled off, and loaded on a drum on CDI-classic
(trade name, made by Esko-Graphics; Nd-YAG laser of 1,060 nm) with
the ultraviolet-ray shielding layer on the photosensitive resin
layer being put outside. The ultraviolet-ray shielding layer on the
photosensitive resin construct was subjected to laser drawing at a
laser power of 20 W and at a drum rotating frequency of 1,600 rpm.
The pattern of the laser drawing used a resolution of 2,800 dpi, a
screen line number of 59 (line/cm), halftones of 1%, 2%, 3%, 5%,
10%, 30%, 50%, 60%, 70%, 80%, 90%, 95%, and 100% (hereinafter
referred to as solid), and concave lines/convex lines of 500 .mu.m
in width. Next, the photosensitive resin construct was laid on a
glass plate of AFP-1500 exposure machine (trade name, made by Asahi
Kasei Chemicals Corp.) with the laser-drawn ultraviolet-ray
shielding layer directed upward; and using an ultraviolet
fluorescent lamp having a center wavelength of 370 nm, the whole
surface was subjected to exposure at 300 to 600 mJ/cm.sup.2, first,
from the support side such that the relief depth of the printing
plate became 0.6 mm. Thereafter, the photosensitive resin construct
was subjected to relief exposure at 8,000 mJ/cm.sup.2 from above
the ultraviolet-ray shielding layer after the drawing. The exposure
intensity at this time was measured using a UV luminometer MO-2
(made by ORC Manufacturing Co., Ltd.) and a UV-35 filter; and the
intensity obtained by the measurement on a glass plate of
ultraviolet rays from the underside lamp, which is on the back
exposure side, was 10.3 mW/cm.sup.2 and the intensity obtained by
the measurement of ultraviolet rays from the upside lamp, which is
on the relief exposure side, was 12.5 mW/cm.sup.2.
[0103] Then, the plate construct was adhered on a cylinder of
AFP-1500 developing machine (trade name, made by Asahi Kasei
chemicals Corp.) with a double-sided adhesive tape, and subjected
to development at a liquid temperature of 25.degree. C. for 5 min
using 3-methoxybutyl acetate as a developing liquid. Further, the
construct was dried at 60.degree. C. for 2 hours. Thereafter, the
whole plate surface was subjected to exposure as post-exposure at
2,000 mJ/cm.sup.2 using a germicidal lamp having a central
wavelength of 254 nm, and successively subjected to exposure as the
post-exposure at 1,000 mJ/cm.sup.2 using an ultraviolet fluorescent
lamp to thereby obtain a flexographic printing plate. Here, the
post-exposure amount by the germicidal lamp was calculated from
illuminance measured using an UV-25 filter of the MO-2
luminometer.
(5) Evaluation Methods
(5-1) Cold Flow Resistance
[0104] The photosensitive resin construct of 3 mm in thickness
obtained in. (3) was cut out into 5 cm.times.5 cm; the thickness
change after the cut-out piece was allowed to stand at 40.degree.
C. for 7 days with the whole surface of the cut-out piece loaded
with a load of 28 g/cm.sup.2 was measured. In the case where the
thickness reduction rate of the photosensitive resin construct in
this measurement exceeded 3.0%, since the plate construct sometimes
deformed when the photosensitive resin construct was stored or
transported, the photosensitive resin construct was defined as
poor; in the case of not less than 2.0% and less than 3.0%, the
construct was defined as good; and in the case of less than 2.0%,
the construct was most favorable and defined as excellent.
(5-2) Transparency of the Photosensitive Resin Composition
[0105] The photosensitive resin component obtained in (3) was
interposed by polyester films of 100 .mu.m, and was subjected to a
pressure by a press at 200 kg/cm at 130.degree. C. for 4 min, using
a spacer, to thereby obtain a construct of 3 mm in thickness. The
haze of the construct was measured using a visible-light haze meter
1001DP (trade name, made by Nippon Denshoku Industries Co., Ltd.).
A lower haze is preferable for excellent printing quality. Making
the haze not more than 20% is important and any construct exceeding
20% was not evaluated for other evaluation items and the construct
was not employed as Examples.
(5-3) Image Reproducibility (Depth of Concave Line of 500
.mu.m)
[0106] The printing plate obtained in (4) was measured for depth of
concave lines of 500 .mu.m in width. A deeper depth of the concave
lines is preferable for maintaining excellent printing quality for
a long time. The depth of not less than 150 .mu.m was defined as
acceptable.
(5-4) Preventing Effect of Printing Plate Surface Smear of the
Printing Plate
[0107] The printing plate obtained in (4) was evaluated for the
preventing effect of the printing plate surface smear of the
printing plate by the following three methods.
(5-4-1) Contact Angle of Water Droplet on the Printing Plate
Surface
[0108] The contact angle of water droplet on the solid surface
obtained in (4) was measured by a droplet method using a solid
liquid interface analyzer DropMaster 500 (trade name, made by Kyowa
Interface Science Co., Ltd.). The printing plate was allowed to
stand for 1 day in a thermohygrostat chamber set at a temperature
of 23.degree. C. and a relative humidity of 50%. Thereafter, using
"FAMAS ver. 1.8.1" as an analysis software, purified water as a
probe solution and a stainless steal-made needle 22G as a needle,
and under the conditions of a discharge time of 200 ms and a
discharge voltage of 4,000 mV, the contact angle at 15 sec after
the purified water contacted with the plate was automatically
measured. A higher contact angle indicates a higher ink
repellency.
(5-4-2) Contact Angle of Water Droplet of the Printing Plate
Surface After Wiped with Ethanol
[0109] The following measurement was conducted as an index of
sustainability of preventing the printing plate surface smear.
First, the printing plate obtained in (4) was put in a
thermohygrostat chamber set at a temperature of 23.degree. C. and a
relative humidity of 50%; and the solid surface was rubbed right
and left for 10 sec with a nonwoven fabric impregnated with
ethanol. At 20 sec after the rubbing finished, the contact angle of
the surface was measured by the same method as in 5-4-1.
(5-4-3) Preventing Effect of Printing Plate Surface Smear
[0110] The preventing effect of the printing plate surface smear
due to printing was evaluated using the printing plate obtained in
(4). Process X Cyan (trade name, made by Toyo Ink Mfg. Co., Ltd.)
was used as a solvent ink; and an OPP film was used as a matter to
be printed. Printing was performed using an Anilox roll of 800 lpi
(its cell volume: 3.8 cm.sup.3/m.sup.2) and 3M1020 (trade name,
made by Sumitomo 3M Ltd.) as a cushion tape, at a printing rate of
100 m/min to thereby print 3,000 m. After the printing, dots on a
3% halftone and 30% halftone and between-dots (concave parts) of
the halftone part of the printing plate were observed with a loupe.
As a result, a plate in which the ink was adhered only on the upper
layer of the dot shoulder was defined as excellent; a plate in
which the ink flowed to the middle part of the dot was defined as
good; and a plate in which the ink flowed to the bottom between
dots was defined as poor.
Example 1
[0111] A flexographic printing plate was obtained according to (3)
and (4) described above by using 70 parts by mass of the sample (a)
obtained in the above as the block copolymer (a), 6 parts by mass
of 1,9-nonanediol diacrylate and 3 parts by mass of 1,6-hexanediol
dimethacrylate as the photopolymerizable monomers (b), 2.0 parts by
mass of 2,2-dimethoxy-phenylacetophenone as the photopolymerization
initiator (c), 0.5 part by mass of KF-8010 as the organosilicon
compound (d), 13.0 parts by mass of a liquid conjugated butadiene
rubber B-2000 (trade name, made by Nippon Soda Co., Ltd., vinyl
content: 90 mol %, viscosity at 30.degree. C.: 20 Pa.s) and a
liquid conjugated butadiene rubber LIR305 (trade name, made by
Kuraray Co., Ltd., its vinyl content: 8 mol %, its viscosity at
30.degree. C.: 40 Pa.s) as plasticizers, and 1.0 part by mass of
2,6-di-t-butyl-p-cresol as a stabilizer.
Example 2
[0112] A flexographic printing plate was obtained as in Example 1,
except for using X-22-161B as the organosilicon compound (d).
Example 3
[0113] A flexographic printing plate was obtained as in Example 1,
except for using KF-410 as the organosilicon compound (d).
Example 4
[0114] A flexographic printing plate was obtained as in Example 1,
except for using SH-710 as the organosilicon compound (d).
Example 5
[0115] A flexographic printing plate was obtained as in Example 1,
except for using X-22-4272 as the organosilicon compound (d)
Example 6
[0116] A flexographic printing plate was obtained as in Example 1,
except for using X-22-3710 as the organosilicon compound (d).
Example 7
[0117] A flexographic printing plate was obtained as in Example 1,
except for using KF-96-100CS as the organosilicon compound (d).
Example 8
[0118] A flexographic printing plate was obtained as in Example 1,
except for using a styrene-butadiene-styrene block copolymer
(hereinafter referred to as SBS), KX-405 (trade name, made by
KRATON), as the block copolymer (a).
Example 9
[0119] A flexographic printing plate was obtained according to (3)
and (4) described above by using 87.5 parts by mass of a
styrene-isoprene-styrene copolymer (hereinafter referred to as
SIS), D-1161 (trade name, made by KRAYTON), as the block copolymer
(a), 6 parts by mass of 1,9-nonanediol diacrylate and 3 parts by
mass of 1,6-hexanediol dimethacrylate as the photopolymerizable
monomers (b), 2.0 parts by mass of 2,2-dimethoxy-phenylacetophenone
as the popolymerization initiator (c), 0.5 part by mass of KF-8010
as the organosilicon compound (d), and 1.0 part by mass of
2,6-di-t-butyl-p-cresol as a stabilizer.
Comparative Example 1
[0120] A flexographic printing plate was obtained as in Example 1,
except for not using the organosilicon compound (d).
Comparative Example 2
[0121] A flexographic printing plate was obtained as in Example 8,
except for not using the organosilicon compound (d).
Comparative Example 3
[0122] A flexographic printing plate was obtained as in Example 9,
except for not using the organosilicon compound (d).
[0123] The flexographic printing plates obtained in Examples 1 to 9
and Comparative Examples 1 to 3 had no fine wrinkles on their
surface and no problem with their appearance. When the printing
plate surfaces of Examples 1 to 9 were rubbed by hand, they had
smoother and less resisting feeling than Comparative Example 1.
Shore A hardnesses of the printing plates obtained in Examples 1 to
9 were measured under the following conditions. The printing plates
were allowed to stand for 1 day in a thermohygrostat chamber of a
temperature of 23.degree. C. and a relative humidity of 50%;
thereafter, the printing plates were measured using a JIS
constant-pressure loader GS-710 (made by TECLOCK Corp., durometer
GS-719G; ASTM D2240A, JIS K6253A, ISO 7619A) and a value after a 15
sec-loading (weight: 1 kg) on a solid surface was defined as Shore
A hardness. As a result, all of the Shore hardnesses were not less
than 50% and not more than 68.degree..
[0124] The evaluation results of the flexographic printing plates
obtained in Examples 1 to 9 and Comparative Examples 1 to 3 as
shown in Table 1.
[0125] It is found that the use of the photosensitive resin
compositions obtained in Examples enables to satisfy a high effect
of preventing the printing plate surface smear of the printing
plates while maintaining the cold flow resistance of the
photosensitive resin constructs, the transparency of the
photosensitive resin compositions and the image reproducibility of
the printing plates, which is the first case for photosensitive
resin compositions containing an organosilicon compound.
[0126] Above all, the printing plates of Examples using silicone
oils containing an organic group containing an amino group or an
aralkyl group exhibited a high preventing effect on the printing
plate surface smear. Among these, Example 1 using a silicone oil
containing an organic group containing an amino group exhibited a
comprehensively most favorable result.
TABLE-US-00001 TABLE 1 Exam- Exam- Exam- Exam- Exam- Exam- Exam-
Exam- Exam- Comp. Comp. Comp. ple 1 ple 2 ple 3 ple 4 ple 5 ple 6
ple 7 ple 8 ple 9 Ex. 1 Ex. 2 Ex. 3 Block copolymer Sample Sample
Sample Sample Sample Sample Sample SBS SIS Sample SBS SIS (a) (a)
(a) (a) (a) (a) (a) (a) (a) Functional group Amino Amino Methyl-
Phenyl Ether Carboxyl Not- Amino Amino None None None of
organosilicon group group styryl group group group modified group
group compound (d) group (5-1) Cold flow 1.5% 1.8% 2.8% 1.5% 2.9%
2.9% 1.5% 1.8% 2.0% 1.5% 1.8% 2.0% resistance Evaluation Excel-
Excel- Good Excel- Good Good Excel- Excel- Excel- Excel- Excel-
Excel- lent lent lent lent lent lent lent lent lent (5-2) Haze of
13% 15% 15% 11% 18% 19% 20% 15% 16% 12% 15% 15% photosensitive
resin composition (5-3) Depth (mm) 230 220 190 240 200 205 180 220
210 230 220 220 of concave line of 500 mm (5-4-1) Contact
94.degree. 94.degree. 95.degree. 88.degree. 88.degree. 88.degree.
88.degree. 94.degree. 94.degree. 85.degree. 85.degree. 83.degree.
angle of water (5-4-2) Contact 97.degree. 96.degree. 95.degree.
86.degree. 85.degree. 85.degree. 85.degree. 96.degree. 95.degree.
85.degree. 85.degree. 83.degree. angle of water (after ethanol-
wiping) (5-4-3) Ink Excel- Excel- Excel- Good Good Good Good Excel-
Excel- Poor Poor Poor repellency lent lent lent lent lent
INDUSTRIAL APPLICABILITY
[0127] The present invention is suitably usable in the field of
photosensitive resin compositions for use in flexographic printing
plates.
* * * * *